This invention refers to the control of emissions to the atmosphere which result when hot coke is pushed from a coke oven. The amount and composition of these emissions vary depending on the physical condition of the coke oven and upon the manner in which it is operated. In a coke oven which is in good condition and in which coking temperatures and duration are proper, the emissions are relatively low in quantity and consist primarily of particulates of coke. When the condition of the oven is poor and/or operating conditions are inadequate, "green coke" is produced. In this case, the emissions consist of coke particles plus a variety of tars and hydrocarbons. The quantity of emissions in the former case may be about 0.25 kg per ton of coke produced; in the latter case it may be 1.0 kg per ton of coke produced.
A battery of coke ovens consists of a number of individual ovens, typically 35 to 70 in number, arranged side by side in a monolithic block of refractory brick. Coking times vary from 16 to 24 hours depending primarily on the condition of the ovens and the type of coke produced Coke is pushed from the ovens and coal charged into the ovens in a pre-determined schedule, the time between successive pushes being roughly equal to the coking time divided by the number of ovens in the battery.
Various pieces of machinery serve to operate a battery of coke ovens including a pusher to push the coke from the oven, a quench car to receive the hot coke and a coke guide to conduct the coke from the oven to the quench car. Each piece of machinery is movable along the length of the battery so that it may be positioned in alignment with the oven which is to be pushed. When the coke emerges from the coke guide it falls a distance into the quench car. The impact of the coke upon the body of the car causes most of the emissions. The ascent of the particles is aided by the rising current of gasses from the incandescent coke.
There are two methods of capturing the emissions which are in current use. Both methods employs a fixed, land-based dust collector. In one method, a duct running the length of the coke battery conducts the gasses from a movable collection hood to the dust collector. This method requires a means for connecting the hood to the duct at each of the numerous coke ovens of the battery. The other method has a large shed or building over the side of the battery that discharges coke, including the tracks for the quench car.
In either method, the dust collector is a large bag house, or a large wet electrostatic precipitator. The former requires the use of a precoat material in order to prevent the tarry products of the particles from sticking to the bags. The latter require an auxillary water treatment system to remove the particles from the water. Both require a large exhaust fan and a method for disposing of the dust which is collected.
Both methods of capturing the dust involve a large installation of equipment which is expensive to install and expensive the operate and maintain. The method using the duct has the additional disadvantage and complication of the multiplicities of connections between the hood and the duct. The shed has the additional disadvantage in that it worsens the atmosphere for the workers who are occupied in the space under it, and in that it accumulates tarry deposits on its inner surfaces.
In an effect to avoid some of the disadvantages of the two land-based methods, two methods using mobile dust collectors have been tried. One method involving a high efficiency steam jet was installed in a number of batteries, but was too complicated and difficult to operate, and was discarded. The other method uses water sprays in the hood in order to capture the dust. The efficiency of collection for this method was too low to meet environment standards, especially when "green coke" is produced. It also has the disadvantage of requiring a system to remove the dust from the spary water.